Glaciation EQ3 > Lesson 4 > Flashcards

Lesson 4 Flashcards

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1
Q

What are the factors that affect the rate of glacial erosion / glacial movement?

A
  • Ice thickness
  • Precipitation levels
  • Rates of ablation
  • Bedrock permeability
  • Ice/slope gradient
  • Basal temperature
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2
Q

How does ice thickness impact glacial erosion?

A

Thicker ice is heavier, leading to more glacial erosion

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3
Q

How does ice thickness impact glacial movement?

A

Plastic flow begins when ice is 50m thick

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4
Q

How does precipitation levels impact glacial movement?

A

Higher snowfall, results in greater accumulation, increasing the rate of movement due to mass balance

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5
Q

How do precipitation levels impact glacial erosion?

A

Higher precipitation leads to greater accumulation and a larger weight of the glacier, this increases erosion

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6
Q

How do rates of ablation impact glacial movement?

A

More meltwater increases basal sliding, therefore increasing movement

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7
Q

How do rates of ablation impact glacial erosion?

A

More movement leads to more erosion

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8
Q

How does bedrock permeability impact glacial erosion?

A

Permeable rocks tend to be softer, therefore more erosion

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9
Q

How does bedrock permeability impact glacial movement?

A

Permeable meltwater can percolate away, slowing the movement of the glacier

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10
Q

How does ice and slope gradient impact glacial movement?

A

Steeper angle results in faster movement

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11
Q

How does ice and slope gradient impact glacial erosion?

A

Steeper gradients and faster movement increase erosion

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12
Q

How does basal temperature impact glacial movement?

A

Colder ice moves slower than warmer ice as it doesn’t deform as easily and sticks to the bedrock

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13
Q

How does basal temperature impact the rates of glacial erosion?

A

It determines whether a glacier slides over its bed with higher basal temperature (high erosion)
Or is frozen to it with lower basal temperature (low erosion)

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14
Q

What is the most important factor in controlling the rate of glacier movement/erosion?

A

Ice and slope gradient

Gravity makes the glacier move

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15
Q

What are the 4 glacial processes?

A
  • erosion
  • entrainment
  • transport
  • deposition
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16
Q

Glacial processes

Erosion

A

The removal of material via plucking, fracture and dilation

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17
Q

Glacial processes

Entrainment

A

Small rock fragments are trapped (entrained) by basal ice freezing around them which then pulls them along

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18
Q

Glacial processes

Transport

A

Rock debris is transported on the surface (supraglacial) and within the ice (englacial) and at the base (subglacial)

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19
Q

Glacial processes

Deposition

A

Glacial till and fluvioglacial debris is deposited by glacial meltwater

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20
Q

What are polygenetic landforms?

A

Landforms that exist from several glacial periods

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21
Q

Describe the 3 steps in the formation of a corrie:

A
  1. Snow accumulates in a nivation hollow; it stays there and builds up year after year where it compresses the ice
  2. Freeze-thaw weathering and plucking of the back wall causes it to deepen, abrasion helps to over deepen the bottom
  3. Eventually, the ice melts, creating the potential for a tarn/lake depending on rock type
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22
Q

What is an arête?

A

Where 2 corries form side by side

(formation same as corrie)

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23
Q

What is a pyramidal peak?

A

Form where 3 or more cirques erode a mountain

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24
Q

How are u-shaped valleys formed?

A

Where a glacier has carved through a pre-glacial mountain valley, straightening, widening and deepening it as it goes

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25
How can you spot a u-shaped valley?
A misfit stream A stream that doesn’t seem to fit the valley it is in
26
How are truncated spurs formed?
When pre-glacial interlocking spurs of a river valley are widened and deepened by glacial ice. Abrasion is the dominant process, as well as some plucking, by which the sides of a valley are eroded to remove spurs by ‘truncating’ them (cutting them off)
27
How are hanging valleys formed?
Where a main glacier has eroded a trough deeper and wider than the smaller glaciers joining it
28
How are ribbon lakes formed?
After de-glaciation, water fills hollows within the glacial trough (often sat on impermeable ground) These hollows are usually found within a change of geology
29
Cirque
30
Arête
31
Pyramidal peak
32
Truncated spurs
33
U-shaped valley / glacial trough
34
Hanging valley
35
Ribbon lake
36
What features are useful for showing ice direction?
Stoss and Lee features
37
What is the stoss side of a Stoss and Lee feature?
The upstream side of the landform
38
What is the ‘lee’ side of a Stoss and Lee feature?
The downstream side of the landform
39
Meso features What are whalebacks?
A streamlined rock knob with symmetrical longitudinal profiles caused by abrasion of both stoss and lee sides
40
Meso features What are whalebacks formed under?
Formed beneath relatively thick, slow, warm-based ice with little meltwater and no basal cavities (means no freeze-thaw or plucking can occur)
41
Whaleback
42
Meso features How are Roche Moutonnees formed?
They are formed between warm-based ice with abundant basal meltwater They form due to abrasion on their stoss side and plucking on their lee side.
43
Roche Moutonnee
44
Meso features What is a crag and tail?
A hill with a tail of softer rock behind on the lee side
45
Meso features How is a crag and tail formed?
Selective erosion and deposition beneath an ice sheet The crag is usually of strong rock that has resisted glacial erosion and forms an obstruction to the ice eroding the lee side
46
Crag and tail
47
Give an example of a crag and tail in the UK
Edinburgh (on top of a crag)
48
Meso features How does a Knock an' Lochan form?
Occurs due to alternating bands of hard and soft rock They are alternating roche moutonnees and eroded hollows (where the softer rock was) often containing small lakes
49
What does cnoc (knock) mean in Gaelic?
A small rock hill
50
What does lochan mean in Gaelic?
Lake
51
Where are Knock an' Lochans found?
East Shetland, Scotland Northern Canada
52
Knock an' Lochan
53
Micro features What are striations?
A series of long, straight parallel lines or grooves scratched onto a bedrock surface by rock fragments lodged in the base of a moving glacier
54
How can striations show ice direction?
They start deeper and get thinner
55
Micro features What are chatter marks?
Crescent-shaped chips in the bedrock, indicating the direction of glacial movement
56
How are chatter marks formed?
As a glacier moves, it drags rock fragments underneath it These stick and jolt across the surface, causing irregular chips and fractures
57
Micro features What are crescentic gouges?
Any curved mark or fracture produced by plucking or chipping of the glaciers bed. Larger than chatter marks
58
How can crescentic gouges show ice direction?
The horns of these gouges point up glacier
59
Why are micro features important?
- Help understand the movement of ice - Help in determining the maximum altitude of glacial erosion
60
Name the glacial sub aerial processes:
- freeze thaw weathering - solution / carbonation - mass movement - meltwater erosion - frost heave
61
Glacial Sub Aerial Processes Explain freeze-thaw weathering
Water enters cracks in the rocks and freezes, water expands by 9%, therefore, it's able to crack and break rock over time
62
Glacial Sub Aerial Processes Freeze thaw: How is talus (scree) formed?
Freeze thaw weathering of slopes
63
What temperatures does scree tend to form between?
+6 and -6 C
64
What trend can be seen on scree slopes?
Particles increase in size downslope
65
What is regolith?
The (green) loose soils on a scree slope
66
How does block weathering happen? What happens to the weathered blocks?
Physical weathering causes cracks to appear in rocks and joints are opened up. Blocks eventually fall onto the talus slope, wearing down and eventually forming boulders
67
Explain solution:
At lower temperatures, CO2 is more soluble and dissolves in rainwater This forms a weak carbonic acid which reacts with limestone, dissolving it
68
Explain meltwater erosion:
Due to weakened chemicals in precipitation and water in glaciers travelling under hydrostatic pressure, certain rocks (like limestone) can be easily eroded
69
What is mass movement?
The large-scale movement of weathered material in response to gravity
70
What are the 5 types of mass movement?
- rock fall - soil creep - landslides - mudflow - slumping
71
What does frost heave cause?
Potholes
72
Explain the process of frost heave:
- Sediment and soil move upwards due to freeze-thaw action in the soil - Larger material (e.g. soil) rises and smaller materials move downwards - Water gets in cracks, worsening the erosion
Glaciation EQ3
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